The following discussion of the background of the invention is intended to facilitate an understanding of the invention. However, it should be appreciated that the discussion is not an acknowledgement or admission that any of the material referred to was published, known or part of the common general knowledge as at the priority date of the application.
A hearing aid is a device used in some forms of deafness to amplify sound before it reaches the auditory organs. Modern hearing aids are electronic and generally comprise a small electronic apparatus that amplifies sound and is worn in or behind the ear to compensate for impaired hearing. They contain a tiny receiver and a transistor amplifier, and are usually battery powered. Some are small enough to fit into the outer ear.
There are three main types of conventional hearing aid. One is the bone-conduction hearing aid. This hearing aid is placed behind the ear and channels sound waves to the adjacent bony part of the skull, which then transmits the vibrations to the auditory nerve of the cochlea. Another main type of hearing aid is the air-conduction hearing aid. This hearing aid amplifies sounds and directs them into the ear toward the tympanic membrane. In recent years, a number of advancements have been made to hearing aids, improving the comfort, sensitivity, and aesthetic quality of the devices. Today, many hearing aids are customized to amplify only those noises (e.g., high frequency) that the user has difficulty hearing. The last main type of hearing aid is the cochlear implant. This type of device has been developed for use by certain severely-profoundly deaf people. They consist of mechanical replacements for ineffective hair cells in the inner ear, which transform sound vibrations into electronic impulses that stimulate the auditory nerve.
Of the air conduction type of hearing aid there are a number of variations of this aid. One such aid is referred to as the Behind The Ear (BTE) aid. This type of aid has a small case that fits behind the ear and conducts and amplifies sound from a directional microphone to the ear canal through an earmold that is custom made. BTEs can be used for mild to profound hearing losses.
Another such air conduction hearing aid is referred to as the In The Ear (ITE) aid. This device fits in the outer bowl of the ear (called the concha) and is sometimes visible when standing face to face with someone. ITE hearing aids are custom made to fit each individual's ear. They can be used in mild to some severe hearing losses. Squealing or whistling caused by sound leaking out of the aid and being amplified again, may be a problem for severe hearing losses. Some modern circuits are able to provide feedback regulation or cancellation to assist with this.
Further variations of the air conduction hearing aid include devices referred to as In The Canal (ITC), Mini Canal (MC) and Completely In Canal (CIC) aids. ITC aids are smaller, filling only the bottom half of the external ear. One usually cannot see very much of this hearing aid when face to face with someone wearing the device. MC and CIC aids are even smaller and are often not visible unless one looks directly into the wearer's ear. They can be used for mild to moderate hearing losses.
Another air conduction hearing aid is referred to as an Open-Fit or Over The Ear (OTE) hearing aid. Usually quite discreet, these are small Behind The Ear (BTE) type devices, with a much finer clear tube that runs down into the ear canal. Inside the ear canal, there is a small soft silicone dome or a moulded acrylic tip that holds the tube in place. There are also devices available which have an external speaker, placed inside the ear canal, and connected to the hearing system itself by a thin cable. Inside the ear canal, there is a small soft silicone dome or a moulded acrylic tip that houses the receiver and holds it in place in the ear canal. Such devices are referred to as Receiver In The Ear (RITE) hearing aids. In these devices, the external speaker allows the apparatus behind the ear to be even smaller.
In The Ear (ITE), In The Canal (ITC), Mini Canal (MC) and Completely In Canal (CIC) type hearing aids have a shell shaped body containing a microphone, amplifier, and receiver. The receiver is a loudspeaker that generates sound in the user's ear canal. One end of the shell type body has a faceplate that includes a battery door, on/off switch, volume control (if available), and microphone opening. Most of the shells for each of these aids are made from ear mold impressions taken from the ear canal and/or concha of the user who will wear the hearing aid. Accordingly, the shell shaped body, which has been moulded to fit the shape of the user's ear canal and/or concha, is inserted into the ear of the user and fits snugly in the user's ear canal and/or concha. The end of the shell shaped body opposite the faceplate has an aperture through which sound generated by the receiver passes into the user's ear canal. Receiver In The Ear (RITE) hearing aids also have a shell shaped body containing a microphone and amplifier. However, the receiver is placed inside the ear canal and is connected to the body by a thin cable. Inside the ear canal, there is a small soft silicone dome or a moulded acrylic tip that houses the receiver and holds it in place in the ear canal.
A hearing professional conducts various audiologic tests including pure-tone thresholds, speech reception thresholds, and speech discrimination scores to define the type, degree, and configuration of hearing loss. In addition, most comfortable loudness and uncomfortable loudness level tests help in determining the patient's dynamic range. All the above tests are used to determine suitable specifications for a user's hearing aid such as frequency response curve, gain, and maximum output.
The functional parameters of a hearing aid such as gain, output, and frequency response can be measured using a standardised test box analyser or tester such as, for example, a Madsen Electronics “Aurical”. This example of a relatively standard hearing aid tester includes a microphone connected via a cable to the measuring device at one end and to a 2-cm3 (2 cc) metal coupler, or any other equivalent device that simulates an ear canal and ear drums, at the other end. The hearing aid is connected to the coupler and the tester tests the performance of the hearing aid such as frequency response, gain, and maximum output of the hearing aid. The coupler simulates the condition of the aid in an ear, but many differences exist between a metal 2-cm3 coupler and the volume and texture of various ear canals and eardrums. Because of these differences, a Real Ear probe-tube measurement is sometimes used to reveal the exact frequency response, gain, and maximum output of the hearing aid in the ear at the site of the eardrum. However, this type of test is not always suitable. It is a difficult test to administer and it is not always possible to insert and maintain an ear probe-tube in the ear of a young child.
Another major problem with a hearing aid tester incorporating a 2-cm3 metal coupler is that it is difficult to marry the sound emitting portion of a hearing aid that is shaped like the concha or ear canal of a person to a fixed shape metal 2-cm3 coupler. For the hearing aid tester to provide accurate, reliable and repeatable tests results the sound emitting portion of the hearing aid must be able to be connected or retained to the metal 2-cm3 coupler with sound emitting portion oriented and located in a precise position relative to the 2-cm3 metal coupler. Effectively, the hearing professional needs to be able to reliably and repeatably replicate the constant relative position of the sound emitting portion relative to the concha and/or ear canal and/or ear drum of the user. In other words, the user's ear concha and/or ear canal shape, configuration and orientation remains constant even after repeated insertion and removal of the hearing aid and, as such, the hearing aid test equipment needs to be able to replicate this feature of the human ear. It is also preferable if there is an air tight seal between the concha or ear canal shaped sound emitting portion of the hearing aid and the coupler in the case of some forms of hearing aid inserted in the concha and/or ear canal.
At present, hearing professionals use a pliable putty type adhesive material to attempt to retain the sound emitting portion to the 2-cm3 metal coupler that in turn is connected the hearing aid tester. One problem with this is that the putty material may not reliably retain the sound emitting portion to the coupler. Another problem is that each time a sound emitting portion of a hearing aid is retained by the pliable adhesive putty to the coupler the relative position and/or orientation of the sound emitting portion to the coupler, which is simulating the structure of the concha and/or ear canal, varies to an uncontrollable degree. Also, key structures of the hearing aid that affect particular components of the response of the hearing aid, such as vents, may be occluded. Because of these variable factors the results provided by the test equipment may be inaccurate and inconsistent. At present, the hearing professional must use their skill and experience to make an educated guess to compensate for this variability in results associated with the shortcomings of available hearing aid test equipment and the 2 cc coupler discussed above.
Accordingly, it would be advantageous to provide an apparatus for connecting a sound emitting portion of a hearing aid that fits into the concha or ear canal of a user such as, but not limited to, any one or more of the In The Ear (ITE), In The Canal (ITC), Mini Canal (MC), Completely In Canal (CIC), Receiver In The Ear (RITE), and Over The Ear (OTE) type hearing aids, to a 2 cc coupler and a hearing aid tester, or any other equivalent device that simulates an ear canal and ear drums, that provides any one or more of the following: effectively and securely receiving and retaining the sound emitting portion of the hearing aid; reliably and repeatably locating and/or orienting the sound emitting portion of the hearing aid relative to the test equipment, and in particular the microphone associated with the test equipment; providing a practical seal between the sound emitting portion of the hearing aid and the test equipment. It would also be advantageous to provide an apparatus that may also enable hearing aid test equipment to more accurately simulate the condition of the hearing aid in the concha or ear canal of a user such that results provided by the hearing aid test equipment may be more accurate in testing the hearing aid.